Question 906407
{{{f(x)=-x^2+10x}}}
{{{f(x)=-1(x^2-10x)}}}
The term to complete the square is {{{(-10/2)^2=25}}}
Add AND subtract 25 INSIDE the parenthesized part of the definition for f.


That is just to get started for putting f(x) into standard form (vertex form).
You do the rest.


Check this lesson and study it to understand how all of this works:
<a href="http://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev">http://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev</a>